The present invention relates to fabric softener compositions adapted for use in the rinse cycle of a laundering operation.
Liquid fabric softening compositions have been known in the art and are widely used by consumers during the wash and rinse cycles of automatic laundry operations. The term "fabric softening", as used herein and as known in the art, refers to a process whereby a desirably soft handle and fluffy appearance are imparted to the fabrics.
Compositions containing quaternary ammonium salts having at least one long chain hydrocarbyl group are commonly used to provide fabric softening benefits when utilized in laundry rinse operations. For example, see U.S. Pat. Nos. 3,349,033; 3,946,115; and 3,644,203.
For most liquid softener compositions containing cationics as active ingredients, the concentration of such cationics has been limited to the range of about 3 to 6% by weight (U.S. Pat. Nos. 3,904,533 and 3,920,565). This low concentration range of cationics is brought forth by the fact that cationics form gels at the concentrations above 8%. At concentrations above 8%, the electrolytes frequently used to lower the viscosity of fabric softeners, e.g., sodium chloride, sodium carbonate, and sodium acetate, are ineffective.
Despite the problem with gelling, efforts have been made to develop concentrated cationic fabric softeners. Smaller packages for the same amount of active ingredients, less bulky containers, and less storage space are reasons for the development of concentrated cationic-containing fabric softeners.
U.S. Pat. No. 3,920,565 discloses a liquid fabric softener containing a soap and cationic softening agents. The concentration of the cationic is from about 2 to 15% by weight. However, it is also noted in this patent that the preferred range is from 2.5 to 6%, in order to avoid gelling problems.
U.S. Pat. No. 3,954,634 discloses a process for forming a stable, low viscosity fabric softener containing 7 to 15% by weight of cationics. The process comprises pre-mixing deionized water and the softening agent, and homogenizing at a pressure of from 500 to 8000 psi. The use of anti-gelling agent is not disclosed in this patent.
U.S. Pat. No. 3,970,596 discloses a liquid detergent composition having an anti-gelling agent comprising a mixture of nitrate and chloride salts. However, the active detergent ingredient disclosed is alpha-olefin sulfonate which is anionic. Furthermore, test runs in this patent showed that, when the nitrate was used alone, gelling resulted.
U.S. Pat. No. 3,554,916 discloses a process of preventing the gelling of detergent compositions containing the product of an alkylaryl sulfonic acid neutralized with an amine by incorporating a small amount of a C.sub.4 to C.sub.8 alcohol. The use of Al(NO.sub.3).sub.3 as an additive resulted in a pourable product. However, it is noted that the detersive compound used here is a neutralized product.
U.S. Pat. Nos. 3,959,155 and 3,958,059 are directed to anti-static compositions. The use of zinc nitrate is disclosed, but the nitrate does not function as an anti-gelling agent.
U.S. Pat. No. 3,953,380 discloses a liquid synthetic heavy-duty laundry detergent composition. An alcohol is used as an anti-gelling agent.
The above-cited references show that there is a need to develop a stable concentrated fabric softening composition which is economical to produce.